Deposition of metal-rich mine tailings, metal smelting, leather tanning, electroplating, emissions from gas exhausts, energy and fuel production, downwash from powerlines, intensive agriculture and sludge dumping are the most important human activities which contaminate soil systems with large amounts of toxic metals. The list of sites contaminated with toxic metals grows larger every year, presenting a serious health problem and a formidable danger to the environment.
In spite of the growing number of metal-contaminated soil sites, the costly process of removing and burying metal-contaminated soils, or isolating the contaminated sites, remain the most commonly used methods for reclaiming metal-contaminated soils.